1. Field of the Invention
The present invention relates to a bicycle hub. More specifically, the present invention relates to a bicycle hub that is mounted on a bicycle frame with a mounting shaft which is affixed to the bicycle frame by a wrenching mechanism.
2. Background Information
In a conventional hub for a bicycle, the hub is installed in a center portion of a wheel of the bicycle. The hub is usually equipped with a hub axle and a hub body. The hub axle is non-rotatably mounted to a frame of the bicycle (for example, to a front fork of the bicycle). The hub body is mounted to an outer perimeter of the hub axle such that the hub body can freely rotate around the hub axle. More specifically, the hub is provided with a pair of bearings, which support the hub body so that the hub body can freely rotate around the hub axle. Furthermore, a pair of male screw portions are formed on axial ends of the outer perimeter of the hub axle so that the hub is mounted to the frame by a pair of nuts that engage with the screw portions at the axial ends of the hub axle. In such a conventional hub, each of the bearings is an angular-type bearing that is equipped with an outer ring and an inner ring. The outer ring includes a ball receiving surface and mounted to the inner perimeter of the hub body. The inner ring includes a ball pushing surface and is screwed into the hub axle. The bearing includes a plurality of rolling components or bearing balls that are installed between the outer ring and the inner ring at predetermined intervals in the circumferential direction of the hub.
In recent years, in order to increase the rigidity of the hub of the mountain bike for downhill use, a hub has been developed that is mounted to the suspension fork with, for example, a mounting shaft of 20 mm that passes through a hub axle as disclosed in Japanese Official Gazette for Kokai Patent No. 3090251A. The hub axle of this type of hub is usually provided with a central hole through which the mounting shaft passes. Moreover, the hub includes a cylindrical hub body that is installed on the outer perimeter of the hub axle, and a pair of rolling bearings that supports the hub body such that the hub body can freely rotate around the hub axle. With this type of hub, the hub axle is non-rotatably coupled to a suspension fork of a bicycle by mounting the mounting shaft such that the mounting shaft passes through the hub axle, and by wrenching the mounting shaft to the suspension fork by a screw at an axial end of the mounting shaft.
When using the hub disclosed in the above mentioned reference, the wrenching torque for wrenching the mounting shaft is usually specified by the manufacturers of the suspension. However, when bicycle retailers and manufacturers wrench the mounting shaft by using the specified torque in the process of mounting the hub to the suspension fork, in some cases, the working face of the bearing (the abutment state between the bearing surfaces and the bearing balls) as well as the rotation of the wheels becomes deteriorated. In other words, by wrenching the mounting shaft to mount the hub on the suspension folk with the specified torque, sometimes the bearing balls and the ball receiving surfaces and/or the ball pushing surface contact each other such that a smooth rotation of the wheel is disturbed. In such cases, the level of torque used in the process of mounting the hub to the frame has to be adjusted to a lower level so that the outer ring and the inner ring rotate with respect to each other with less resistance. In such cases, the hub cannot be mounted onto the frame by utilizing the specified torque.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle hub. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.